Bug#746963: check-missing-firmware only works with FAT filesystems but does not mention this

[Chris Bainbridge <chris.bainbridge@gmail.com>]

Package: debian-installer

The installer says "The firmware can be loaded from removable media,
such as a USB stick or floppy".

As a Linux user, it would seem reasonable to assume that it might work
with ext2 formatted media, so the fact that it does not, should be
stated:

"The firmware can be loaded from MSDOS/FAT-formatted removable media,
such as a USB stick or floppy"

 or

"The firmware can be loaded from MSDOS filesystem on removable media,
such as a USB stick or floppy"